1. Field of the Invention
The present invention relates to an optical state modulation apparatus for applying an optical intensity modulation on an image displayed on a display screen so as to generate an optical state variation that is visible in a recorded image obtained through unauthorized image-capturing of the displayed image and interferes viewing of the recorded image. The present invention also relates to a display system and an optical state modulation method, which may be realized with the optical state modulation apparatus.
2. Description of the Related Art
A technology for preventing unauthorized recording of an image displayed on a display screen is disclosed in U.S. Pat. No. 6,018,374. The above technology disclosed in U.S. Pat. No. 6,018,374 takes into account the difference in imaging characteristic between human vision and an image-capturing camera, and utilizes infrared light as a means of preventing such unauthorized recording of the displayed image. Specifically, the above technology employs a system having an infrared light projector that is placed in the vicinity of an image projector or any other position far from the display screen. In the system, infrared light is projected from the infrared light projector to the display screen so as to allow infrared light reflected off the display screen to fall upon an image-capturing apparatus operated by a person who is conducting an image/video piracy. In other words, the system used in the above technology enables an infrared image unrelated to a feature film/video program image to be recorded in a recorded image obtained through the image/video piracy. Accordingly, a quality of the recorded image obtained through the image/video piracy may be damaged, and a location at which the image/video piracy has been conducted may be also identified, as the case may be. It is a matter of course that the infrared light is not perceived by the human vision, so that a viewer finds no difficulty in enjoying the viewing of the feature film/video image.